First tab is working great. However, when user selects the number from the drop down menus in the second tab and clicks the "Berekenen" button, my php file does the calculation and writes the results just below the boxes. However, since the page is calling itself once the submit button is clicked, the default tab, which is the first one, is becoming active again. You will understand what I mean once you go to my website and use it. I just want artificially activate the second tab. How can I do it?